The Influence of Strata on the Nutrient Recycling within a Tropical Certified Organic Coffee Production System

In tropical Bolivia coffee plantations, the plant community can be separated into high (trees), middle (coffee), and low (weed) strata. Understanding the importance of each stratum is critical for improving the sustainability of the system. The objective of this study was to determine the importance of strata on nutrient recycling. Litter falls from the upper and middle strata were collected monthly using cone-shaped traps and divided by species into leaves, branches, flowers, and fruits. Dry biomass additions to the soil from high and middle strata totaled 12,655 kg (ha yr)−1 annually. About 76% of the biomass was provided by plants of the genus Inga (I. adenophylla and I. oerstediana). The middle stratum (Coffea arabica L.) provided 24% litterfall biomass. This stratum also produced 1,800 kg coffee bean per ha (12% moisture) which sold for $2.94 kg−1. In the lower stratum, Oxalis mollissima returned 36 kg N ha−1, while Solanum nodiflorum returned 49 kg K ha−1, and Urticasp. returned 18 kg Ca ha−1. The nutrients recycled through plants in three strata exceeded the amount of nutrients removed in green coffee beans

Nitrogen Rate, Landscape Position, and Harvesting of Corn Stover Impacts on Energy Gains and Sustainability of Corn Production Systems in South Dakota

The harvesting of plant biomass in excess of the soil organic carbon (SOC) maintenance requirement can produce short-term economic benefi ts at the cost of long-term sustainability. Th e objective of this study was to assess the impact of corn (Zea mays L.) harvesting approach, N rate, and simulated landscape positions on estimated long-term SOC maintenance, profi tability, and the energy effi ciency of no-till corn grown in eastern South Dakota. Th e 3-yr experiment (2002–2004) contained four N rates (0, 56, 112, and 168 kg N ha−1), two simulated landscape positions (shoulder and backslope), and two harvesting methods (grain with 100% stover returned or grain + 40% corn stover returned). No-tillage was used at the site. Energy gains (out – input), for a cropping system where corn grain or corn grain plus stover was sold for ethanol production, were calculated. Profi tability was estimated and SOC turnover was simulated using the annual time-step model, SOCt = SOCt-1 + kNHCNHC – ksoc SOCt-1, where SOCt was SOC at time t, SOCt-1 was SOC at the sampling date before time t, kNHC was rate that nonharvested carbon (NHC) was converted to SOC, and ksoc was the rate that SOC was converted to CO2. Tillage impacts on kSOC was estimated with the model ksoc [g SOC-C (g SOC year)−1] = 0.0115 + 0.00631(tillage events). When only grain was harvested, the highest and lowest energy gains and fi nancial were associated with the 112 kg N ha−1 (46.6 GJ ha−1 and $427 ha−1) and the 0 kg N per ha−1 (37.5 GJ ha−1 and$192 ha−1) treatments, respectively. Applying more than 112 kg N ha−1 did not increase energy gains or fi nancial returns. Profi ts were increased by 60% when corn stover was harvested for ethanol production and lower yielding simulated shoulder/summit position had a lower energy gain (59.3 GJ ha−1 and $425 ha−1) and fi nancial return than the backslope position (66.3 GJ ha−1 and$614 ha−1). Th e SOC sustainability analysis suggests that the ability of a system to maintain SOC depends on many factors including the amount of nonharvested carbon returned to the site, and the amount of carbon contained in the soil

Agroforestry systems, nutrients in litter and microbial activity in soils cultivated with coffee at high altitude

Agroforestry systems are an alternative option for sustainable production management. These systems contain trees that absorb nutrients from deeper layers of the soil and leaf litter that help improve the soil quality of the rough terrain in high altitude areas, which are areas extremely susceptible to environmental degradation. The aim of this study was to characterize the stock and nutrients in litter, soil activity and the population of microorganisms in coffee (Coffea arabica L.) plantations under high altitude agroforestry systems in the semi-arid region of the state of Pernambuco, Brazil. Samples were collected from the surface litter together with soil samples taken at two depths (0-10 and 10-20 cm) from areas each subject to one of the following four treatments: agroforestry system (AS), native forest (NF), biodynamic system (BS) and coffee control (CT).The coffee plantation had been abandoned for nearly 15 years and, although there had been no management or harvesting, still contained productive coffee plants. The accumulation of litter and mean nutrient content of the litter, the soil nutrient content, microbial biomass carbon, total carbon, total nitrogen, C/N ratio, basal respiration, microbial quotient, metabolic quotient and microbial populations (total bacteria, fluorescent bacteria group, total fungi and Trichoderma spp.) were all analyzed. The systems thatwere exposed to human intervention (A and BS) differed in their chemical attributes and contained higher levels of nutrients when compared to NF and CT. BS for coffee production at high altitude can be used as a sustainable alternative in the high altitude zones of the semi-arid region in Brazil, which is an area that is highly susceptible to environmental degradation

Grassland Retention in the North America Midwest After Periods of High Commodity Prices and Climate Variability

The conversion of grassland, wetlands, and forest to croplands may contribute environmental degradation and diminished sustainability. This study determined the impact of land use change from 2006 to 2012 and from 2012 to 2014 on the cultivation suitability of grasslands that were not converted to cropland. The model system, which includes Nebraska and South Dakota, was selected because it contains climatic conditions ranging from humid continental to semiarid and a large number of farms that produced both crops and livestock. During the study, commodity prices reached historically high values, and a severe drought occurred in 2012. Land use benchmarks were obtained by visually identifying land use at 81,600 sample sites in high-resolution remote sensing images obtained from the National Agricultural Imaging Program. Sampling sites with Land Capability Class values ≤4 were identified as suitable for cultivation if appropriate practices were followed. In 2006, 2012, and 2014, grasslands accounted for 11.0, 10.76, and 10.78 million ha in Nebraska, respectively, whereas in South Dakota, grasslands accounted for 12.12, 11.65, and 11.69 million ha, respectively. In Nebraska, the percentage of grasslands relative to working lands (grassland + croplands) decreased from 60.6% in 2006 to 58.9% in 2014, whereas in South Dakota the percentage of grassland decreased from 69.1% in 2006 to 66.0% in 2014. In eastern Nebraska and South Dakota, 74.1% of the nonconverted grasslands in 2012 were suitable for crop production. Lower-than-expected conversion rates were attributed to a growing interest in land stewardship and a desire to maintain income diversification